Stretch wrap films

ABSTRACT

A method for wrapping a multilayer, thermoplastic stretch wrap film containing at least three polymeric film layers and comprised of an inner polymeric layer. The inner polymeric layer comprises a blend of a low polydispersity polymer and either a high pressure low density polyethylene resin, a very low density polyethylene resin or a combination thereof. The low polydispersity polymer has a polydispersity of from about 1 to about 4, a melt index (I 2 ) of from about 0.5 to about 10 g/10 min., and a melt flow ratio (I 20  /I 2 ) of from about 12 to about 22. The high pressure low density polyethylene resin has a melt index of from about 1 to about 10 g/10 min., and a density of from about 0.9 to about 0.935 g/cm 3 . The very low density polyethylene resin has a melt index of from about 0.5 to about 5 g/10 min., and a density of from about 0.880 to about 0.912 g/cm 3 . The stretch wrap film may include a first layer and a second layer. The first and second layers may comprise a polymer of two or more monomers, wherein a first monomer is ethylene, in a major amount by weight, and a second monomer is an alpha olefin of from about 3 to about 12 carbon atoms, in a minor amount by weight. If the first and second layers are outer layers, they have a cling force to each other of at least about 140 grams/inch. The stretch wrap film has a maximum stretch of at least 340% and a F-50 dart drop value of at least about 150 g/mil. It is contemplated that additional outer layers may be added such an outer high cling layer or an outer slip layer, as well as additional inner layers.

FIELD OF THE INVENTION

The present invention is directed to stretch wrap films and methods fortheir use. In particular, the present invention is directed to stretchwrap films having high puncture resistance, high elongation to break,high force to stretch the film, high cling force, and overall strength.

BACKGROUND OF THE INVENTION

The use of thermoplastic stretch wrap films for the overwrap packagingof goods, and in particular, the unitizing of palleted loads is acommercially significant application of polymer film, includinggenerically, polyethylene. Overwrapping a plurality of articles toprovide a unitized load can be achieved by a variety of techniques. Inone procedure, the load to be wrapped is positioned upon a platform, orturntable, which is made to rotate and in so doing, to take up stretchwrap film supplied from a continuous roll. Braking tension is applied tothe film roll so that the film is continuously subjected to astretching, or tensioning, force as it wraps around the rotating load inoverlapping layers. Generally, the stretch wrap film is supplied from avertically arranged roll positioned adjacent to the rotating palletload. Rotational speeds of from about 5 to about 50 revolutions perminute are common. At the completion of the overwrap operation, theturntable is completely stopped and the film is cut and attached to anunderlying layer of film employing tack sealing, adhesive tape, sprayadhesives, etc. Depending upon the width of the stretch wrap roll, theload being overwrapped can be shrouded in the film while the verticallyarranged film roll remains in a fixed position. Alternatively, the filmroll, for example, in the case of relatively narrow film widths andrelatively wide pallet loads, can be made to move in a verticaldirection as the load is being overwrapped whereby a spiral wrappingeffect is achieved on the packaged goods.

Another wrapping method finding acceptance in industry today is that ofhand wrapping. In this method, the film is again arranged on a roll,however, it is hand held by the operator who walks around the goods tobe wrapped, applying the film to the goods. The roll of film so used maybe installed on a hand-held wrapping tool for ease of use by theoperator.

Certain applications of stretch wrap films require that the film havesuperior cling characteristics in its applied stretched state and havesuperior slip characteristics when loaded beside other wrapped articles.These types of films are referred to as "cling/slip" films and arecommonly used in the shipping of carpet and fabric rolls.

Some of the properties desired of a good stretch wrap film are asfollows: good cling or cohesion properties of inside/outer surfaces,optional slip between outer layers, high puncture resistance, high tearresistance in the transverse direction, good machine direction tearresistance, good transparency, low haze, low stress relaxation withtime, high resistance to transverse tear especially when under machinedirection tension, producible in thin gauges, low specific gravity andthus high yield in area per pound, good tensile toughness, high machinedirection ultimate tensile strength, high machine direction ultimateelongation, and low modulus of elasticity.

Physical properties which are particularly significant for thesuccessful use of thermoplastic films in stretch wrap applicationsinclude their puncture resistance, their elongation characteristics,their toughness and their resistance to tearing while under tension. Ingeneral, tensile toughness is measured as an area under a stress-straincurve developed for a thermoplastic film and it may be considered as thetensile energy absorbed, expressed in units of ft. lbs./cu.in. toelongate a film to break under tensile load. In turn, this toughnesscharacteristic is a function of the capacity of such films to elongate.The process of stretching the film decreases that capacity. Accordingly,the stretch wrap process will decrease the toughness of the film whileit is in its stretched condition as an overwrap as compared to itsunstretched form. Generally this loss of toughness is proportional tothe amount of stretch imparted to the film as it is overwrapping a loadof goods.

Currently, different grades of stretch wrap films are commonly marketedfor different end uses according to overall film properties. Forexample, certain stretch wrap films having superior properties for loadretention are characterized by requiring a higher force to stretch thefilm. However, such load retention films generally have poor puncturecharacteristics at such stretch conditions. On the other hand, certainstretch wrap films having superior puncture resistance properties havelow load retention properties, thus limiting their use.

The present invention is beneficial in conjunction with applications,such as automated stretch wrappers that are designed for the highthrough-put segment of the market, that typically run in excess of 22revolutions per minute. At these high speeds, many commerciallyavailable stretch films experience catastrophic failure due to the highstrain rate.

A need exists for a superior stretch wrap film with high speedextensibility in the high speed market that will not have a catastrophicfailure. A need exists to develop superior stretch wrap filmscharacterized by having excellent load retention characteristics,puncture resistance characteristics, maximum stretch, inside to outersurface cling, and, if applicable, slip properties between outer layersand against other surfaces. Such films could be used in a wider varietyof end applications and, thus, not unduly limit users of stretch wrapfilms to selectively choosing a film based on its properties prior toinitiating a stretch wrap application.

SUMMARY OF THE INVENTION

The present invention is a multilayered film which has excellent cling,tear, load retention, maximum stretch and puncture resistanceproperties. The films of the present invention have improved theseproperties without undue degradation of other important film properties.

The stretch wrap film of the present invention is a multilayer filmconstruction comprised of at least three layers and having at least oneinner polymeric layer. The stretch wrap films of the present inventionmay be used in cling/cling and slip/cling film applications.

The inner polymeric layer of the inventive film comprises a blend ofabout 70 wt. % to about 98 wt. % of a low polydispersity polymer andabout 2 wt. % to about 30 wt. % of a high pressure low densitypolyethylene resin (HPLDPE) and/or a very low density polyethylene resin(VLDPE). The low polydispersity polymer has a polydispersity of fromabout 1 to about 4, a melt index (MI), defined as the I₂ value, of fromabout 0.5 to about 10 g/10 min., and a melt flow ratio (I₂₀ /I₂) of fromabout 12 to about 22. The low polydispersity polymer used to constructthe inner polymeric layer is preferably produced utilizing metallocenecatalyst polymerization techniques. The HPLDPE resin has a melt index offrom about 1 to about 10 and a density of from about 0.9 to about 0.935g/cm³, and the VLDPE resin has a melt index of from about 0.5 to about 5g/10 min, and a density of from about 0.880 to about 0.912 g/cm³.

The inner polymeric layer may comprise additional resins with the abovedescribed resins. In addition, the multilayer film may be constructedwith additional inner layers. For instance, additional inner polymericlayers may be incorporated adjacent to said first inner polymeric layer.The additional inner polymeric layer(s) are preferably constructed withthe same or a different blend of metallocene-catalyzed polyethyleneresins with the HPLDPE and/or VLDPE as the first inner polymeric layer.

The stretch wrap film of the present invention may include first andsecond layers. The first and second layers may be constructed of olefinpolymer resins. These first and second layers are preferably constructedwith a copolymer or a terpolymer of ethylene and a minor amount of atleast one alpha olefin of from about 3 to about 12 carbon atoms. If thefirst and second layers are outer layers, then they have a cling forceto each other of at least about 140 g/inch.

Additional layers may be incorporated in the stretch wrap film such asan outer high cling layer that may be located on an outer surface of thefirst layer or on an outer surface of the inner polymeric layer. Theouter high cling layers are defined herein as layers having a clingforce to each other of at least about 300 grams/inch. Additionally, anouter slip layer may be located on an opposing side of the outer highcling layer.

The multilayer films of the present invention have been found to displayunexpectedly superior film properties compared to other filmconstructions, surprisingly without undue degradation of other importantfilm properties. The incorporation of HPLDPE and/or VLDPE into the innerpolymeric layer has produced an overall film having a F-50 dart dropvalue of at least about 150 g/mil and a maximum stretch of at leastabout 340%.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a three layer cling/cling film constructed in accordancewith the present invention;

FIG. 2 shows a four layer cling/cling film constructed in accordancewith the present invention;

FIG. 3 shows a three layer high cling/cling film constructed inaccordance with the present invention;

FIG. 4 shows a four layer high cling/cling film constructed inaccordance with the present invention;

FIG. 5 shows a three layer high cling/slip film constructed inaccordance with the present invention; and

FIG. 6 shows a four layer high cling/slip film constructed in accordancewith the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The stretch wrap film of the present invention is a multilayer filmconstruction comprising at least three layers and including at least oneinner polymeric layer. These multilayer stretch wrap films can beprepared as cast films by conventional coextrusion techniques. Thestretch wrap films of the present invention may be used in cling/clingand slip/cling film applications.

Inner Polymeric Layer

The multilayer stretch wrap films of the present invention areconstructed with at least one inner polymeric layer. The inner polymericlayer may be a blend of a polymer having a low polydispersity and aHPLDPE resin. Alternatively, the inner polymeric layer may be a blend ofa low polydispersity polymer and a VLDPE resin. Lastly, the innerpolymeric layer may be a blend of a low polydispersity polymer and aHPLDPE resin and a VLDPE resin.

The low polydispersity polymer may be prepared from a partiallycrystalline polyethylene resin that is a polymer prepared with ethyleneand at least one alpha olefin monomer, e.g., a copolymer or terpolymer.The alpha olefin monomer generally has from about 3 to about 12 carbonatoms, preferably from about 4 to about 10 carbon atoms, and morepreferably from about 6 to about 8 carbon atoms. The alpha olefincomonomer content is generally below about 30 weight percent, preferablybelow about 20 weight percent, and more preferably from about 1 to about15 weight percent. Exemplary comonomers include propylene, 1-butene,1-pentene, 1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-octene,1-decene, and 1-dodecene.

The low polydispersity polymer generally has the characteristicsassociated with an LLDPE material, however it has improved properties asexplained more fully below. The low polydispersity polymer definedherein has a density of from about 0.88 to about 0.94 g/cm³, preferablyfrom about 0.88 to about 0.93 g/cm³, and more preferably from about 0.88to about 0.925 g/cm³.

The average molecular weight of the low polydispersity polymer cangenerally range from about 20,000 to about 500,000, preferably fromabout 50,000 to about 200,000. The molecular weight is determined bycommonly used techniques such as size exclusion chromatography or gelpermeation chromatography. The low polydispersity polymer should have amolecular weight distribution, or polydispersity, (M_(w) /M_(n), "MWD")within the range of about 1 to about 4, preferably about 1.5 to about 4,more preferably about 2 to about 4, and even more preferably from about2 to about 3. The ratio of the third moment to the second moment, M_(z)/M_(w), is generally below about 2.3, preferably below about 2.0, andmore typically in the range of from about 1.6 to about 1.95. The meltflow ratio (MFR) of these polymers, defined as I₂₀ /I₂ and as determinedin accordance to ASTM D1238, is generally from about 12 to about 22,preferably from about 14 to about 20, and more preferably from about 16to about 18. The melt index (MI), defined as the I₂ value, should be inthe range of from about 0.5 to about 10 g/10 min., preferably from about1 to about 5 g/10 min. as determined by ASTM D1238.

Useful low polydispersity polymers are available from, among others, DowChemical Company and Exxon Chemical Company who are producers of singlesite or constrained geometry catalyzed polyethylenes. These polymers arecommercially available as the AFFINITY and EXXACT polyethylenes (seePlastics World, p.33-36, Jan. 1995), and also as the ENHANCEDPOLYETHYLENE and EXCEED line of resins. The manufacture of suchpolyethylenes, generally by way of employing a metallocene catalystsystem, is set forth in, among others, U.S. Pat. Nos. 5,382,631,5,380,810, 5,358,792, 5,206,075, 5,183,867, 5,124,418, 5,084,534,5,079,205, 5,032,652, 5,026,798, 5,017,655, 5,006,500, 5,001,205,4,937,301, 4,925,821, 4,871,523, 4,871,705, and 4,808,561, each of whichis incorporated herein by reference in its entirety. These catalystsystems and their use to prepare such copolymer materials are also setforth in EP 0 600 425 A1 and PCT applications WO 94/25271 and 94/26816.The low polyethylene polymers thus produced generally have a crystallinecontent in excess of at least 10 weight percent, generally in excess ofat least 15 weight percent.

The above patents and publications generally report that these catalystscontain one or more cyclopentadienyl moieties in combination with atransition metal. The metallocene catalyst may be represented by thegeneral formula C_(c) MA_(a) B_(b) wherein C is a substituted orunsubstituted cyclopentadienyl ring; M is a Group 3-10 metal orLanthanide series element, generally a Group IVB, VB, or VIB metal; Aand B are independently halogen, hydrocarbyl group, or hydrocarboxylgroups having 1-20 carbon atoms; a=0-3, b=0-3, and c=1-3. The reactionscan take place in either gas phase, high pressure, slurry, or solutionpolymerization schemes.

According to one embodiment, at least one of the inner polymeric layercomprises a low polydispersity polymer which is blended with a HPLDPEresin. The HPLDPE resins have a density of from about 0.9 to about 0.935g/cm³ and preferably a density of from about 0.915 to about 0.925 g/cm³.The HPLDPE resins have a melt index (I₂) of from about 0.5 to about 10,preferably from about 1 to about 5, and most preferably from about 1 toabout 2.5 g/10 min. The HPLDPE resins comprise from about 2 to about 30wt. % of the inner polymeric layer with the preferred range of fromabout 5 to about 15 wt. % of the inner polymeric layer. It is preferredto maintain the level of the low polydispersity polymer to at least 70weight percent of the inner polymeric layer. Additional, material may beincorporated with the blend of the low polydispersity polymer and theHPLDPE resin.

Alternatively, the inner polymeric layer of the present inventioncomprises a blend of a low polydispersity polymer and a VLDPE resin. TheVLDPE resins have a density ranging from about 0.880 to about 0.912g/cm³, more commonly from about 0.89 to about 0.91 g/cm³, and a meltindex (I₂) of from about 0.5 to about 5 g/10 min., and preferably fromabout 1 to about 3 g/10 min. The VLDPE comprises from about 2 to about30 wt. % of the inner polymeric layer with the preferred range of fromabout 15 to about 25 wt. % of the inner polymeric layer. It is preferredto maintain the level of the low polydispersity polymer to at least 70weight percent of the inner polymeric layer. Additional materials may beincorporated with the blend of the low polydispersity polymer and theVLDPE resin.

According to another embodiment, the inner polymeric layer(s) comprisesa blend of a low polydispersity polymer with the above described HPLDPEresins and VLDPE resins.

The inner polymeric layer(s) are preferably at least about 60 wt. % ofthe stretch wrap film and preferably at least about 70 wt. % of thestretch wrap film.

First and Second Layers

The present invention may include first and second layers. The first andsecond layers of the stretch wrap films of the present invention may beconstructed of olefin polymer resins. Suitable polyethylene resins arethose ethylenic copolymers that comprise a major proportion by weight ofethylene copolymerized with a minor proportion by weight of an alphaolefin monomer containing about 3 to about 12, preferably about 4 toabout 10, and more preferably about 4 to about 8, carbon atoms. Theseresins have a polydispersity which is preferably in the range of fromabout 3 to about 7.

Ethylenic copolymers may be those commonly referred to as linear lowdensity polyethylenes (LLDPE). Preferably the ethylenic copolymersemployed are those having from about 1 to about 20, preferably fromabout 1 to about 10 weight percent of said higher alpha olefin monomercopolymerized therein. In addition, the alpha olefin monomer employed inthe ethylenic copolymer may be selected from the group consisting of1-butene, 3-methyl-1-butene, 3-methyl-1-pentene, 1-hexene,4-methyl-1-pentene, 3-methyl-1-hexene, 1-octene and 1-decene.Particularly preferred are the 1-hexene alpha olefins. The LLDPE resinsare prepared at relatively low pressures employing coordination-typecatalysts. Reference may be made to U.S. Pat. Nos. 3,645,992, 4,076,698,4,011,382, 4,163,831, 4,205,021, 4,302,565, 4,302,566, 4,359,561 and4,522,987 for more details of the manufacture and properties of LLDPEresins including those which are particularly useful herein.

The polyethylene resins that are desired to be used as the first andsecond layers in films of the present invention are those that arefunctionally defined as providing a cling force of at least about 140,generally at least about 180, preferably at least about 200, and morepreferably about 220 grams/inch as determined by the ASTM D 5458-94 testas long as the first and second layers are the outer layers. Generally,the cling force of the outer first and second layers will be in therange of from about 140 to about 280 grams/inch. Common LLDPE resinsthat can be used to form the first and second layers include thosehaving a relatively high weight percentage of n-hexane extractables, asmeasured by the n-hexane extractables method of 21 C.F.R. 177.1520.Generally, the LLDPE used in the first and second layers herein willcontain from about 2 to about 10, preferably from about 2 to about 8,more preferably from about 2.5 to about 5, weight percent of n-hexaneextractables.

The LLDPE resins that can be used in the first and second layers hereinhave a density ranging from about 0.890 to about 0.940 g/cm³, morecommonly from about 0.90 to about 0.93 g/cm³, and a melt index (I₂) offrom about 1 to about 10 g/10 min. as determined by ASTM D1238.Particularly preferred are those LLDPE resins possessing densitieswithin the range of from about 0.915 to about 0.920 g/cm³ and a meltindex within the range of from about 2.0 to about 5.0 g/10 min. asdetermined by ASTM D1238. Examples of such LLDPE resins include thoseset forth in U.S. Pat. No. 5,273,809, which is incorporated herein byreference in its entirety.

The LLDPE resins that can be used in the first and second layers can beblended with minor amounts, e.g., up to about 40 weight percent total,of one or more other suitable resins to achieve a desired range ofphysical/mechanical properties in the film product. Thus, for example,such resins as ethyl vinyl acetate (EVA) copolymer, high pressure lowdensity polyethylene (HPLDPE), and other LLDPE resins may be used forblending to obtain useful mixtures for forming the first and secondlayers of the films of this invention.

The LLDPE resins that can be used in the first and second layers hereincan also contain known and conventional cling additives to augment thecling property that, at least in the case of the particularly preferredresins, is inherently exhibited. Examples of useful cling additivesinclude poly-isobutylenes having a number average molecular weight inthe range from about 1,000 to about 3,000, preferably about 1,200 toabout 1,800, as measured by vapor phase osmometry, amorphous atacticpolypropylenes, e.g., those having an average molecular weight of about2000, and polyterpenes and ethylene-vinyl acetate copolymers containingfrom about 5 to about 15 weight percent copolymerized vinyl acetate. Theoptional cling additive may be present in the first and second layers ina concentration of from about 0.5 to about 10 weight percent of theresin. Of course, other conventional film additives such asantioxidants, UV stabilizers, pigments, dyes, etc., may be present inthe usual amounts.

It is preferred to utilize the LLDPE resins that contain relatively highweight percentages of n-hexane extractables for both the first andsecond layers due to overall performance results. However, one or bothof the first and second layers may comprise, for example, a firstethylene monomer and a second monomer that comprises an acrylate. Onexample is an ethylene-acrylate (EA) polymer film shown in U.S. Pat. No.5,049,423, which is incorporated herein by reference in its entirety.These EA polymers generally have an acrylate content between about 2 toabout 40%, preferably between about 10 to about 35%, by weight of the EApolymer. The acrylate useful in these polymers are those generally knownin the art, preferably methyl, ethyl, and n-butyl acrylate. Other knowncling layers are contemplated for the present invention.

Either or both of the outer surfaces of the first and second layers canbe treated by such known and conventional post-forming operations ascorona discharge, chemical treatment, flame treatment, etc., to modifythe printability or ink receptivity of the surface(s) or to impart otherdesirable characteristics thereto.

Additional Layers

Additional layers are contemplated in the stretch wrap film of thepresent invention. For example, the stretch wrap film may comprise anouter high cling layer. The outer high cling layer may be located on anouter surface of a first layer or on an outer surface of an innerpolymeric layer. The outer high cling layer provides a cling force of atleast about 300 grams/inch as determined by the ASTM D5458-94 testmethod. Preferably, the outer high cling layer provides a cling force ofat least about 350 grams/inch and is constructed in a manner similar tothat described above with the first and second layers. The outer highcling layer will typically be a pure resin in order to obtain the highercling forces. Some examples of high cling resins are resins such as EApolymers discussed above and very low density polyethylenes (VLDPE). TheVLDPE resins typically have a density of from about 0.88 to about 0.912g/cm³ and preferably from about 0.89 to about to about 0.91 g/cm³, and amelt index (I₂) of from about 0.5 to about 5 g/10 min. and preferablyfrom about 1 to about 3 g/10 min.

The stretch wrap film of the present invention may also comprise anouter slip layer which may be constructed of various resin materialssuitable for such purposes. Examples of such resins include polyolefinresins and copolymers of polyolefins such as polyethylene,polypropylene, and combinations thereof. Suitable polymer resinsadditionally include copolymers of polyethylene with minor amounts ofother C₄₋₁₀ olefins, particularly C₆₋₈ polyolefins. Preferredpolyethylenes include HPLDPE resins having a density of from about 0.92to about 0.94 g/cm³, and a melt index (I₂) of from about 1.0 to about4.0 g/10 min., and LLDPE resins having a density of from about 0.925 toabout 0.945 g/cm³, and a melt index of from about 2.0 to about 5.0 g/10min. Preferred polymers include polypropylenes, preferably isotactic,having a density of from about 0.89 to about 0.91 g/cm³, and a meltindex (I₂) of from about 5 to about 25 g/10 min. as determined by ASTMD1238.

The outer slip layer may include any of several anticling, slip orantiblock additives to improve the slip characteristics of the layer.Such additives include silicas, talcs, diatomaceous earth, silicates,lubricants, etc. These additives are generally blended with the resinmaterial in an amount of from about 100 to about 20,000 ppm. When anouter slip layer is present in the stretch wrap film, an outer highcling layer as described above will be located as an opposing layer.

Additionally interior layers are also contemplated in the presentinvention to provide barrier properties or cost reductions.

The stretch wrap films of the present invention can be constructed tocontain a plurality of layers of the film in various combinations.According to one embodiment, the stretch wrap film is of an A/BC/Aconstruction (see FIG. 1) wherein the film layers (10) are the first andsecond layers (layers A), film layer (20) is the inner polymeric layerwhich comprises a blend of a low polydispersity polymer (resin B) andeither a HPLDPE resin, a VLDPE resin, or a combination thereof (resinsC). According to another embodiment, the stretch wrap film is anA/BC/BC/A construction wherein film layers (10) and (20) are the same asdescribed above and film layer (30) comprises a blend of resins B and C.The inner polymeric layers (20,30) may be constructed with the sameresins or with different resins to obtain the desired properties of themultilayer film.

Other types of multi-layered constructions are contemplated such as aD/BC/A construction and a D/A/BC/A construction depicted in respectiveFIGS. 3 and 4 where film layer (40) is an outer high cling layer (layerD). In addition, a D/BC/E construction and a D//BC/A/E construction arecontemplated and depicted in respective FIGS. 5 and 6 where film layer(50) is an outer slip layer (layer E).

Stretch Wrap Properties

The overall properties of the stretch wrap films of the presentinvention are such that they have a cling force of at least about 140,generally at least about 180, preferably at least about 200, and morepreferably at least about 220 grams/inch as determined by ASTM D5458-94.Generally, the cling force of the film will be in the range of fromabout 140 to about 280 g/inch. However, if an outer high cling layer isused the film, the cling force will be generally in the range of fromabout 300 to about 350 g/inch as determined by ASTM D5458-94.

The overall stretch wrap films have relatively high puncture resistance,as measured by the F-50 dart drop test procedure (ASTM D1709). It is theexperience of those skilled in the art that the F-50 dart drop test iswell correlated to the end use puncture resistance of stretch wrapfilms. The F-50 dart drop of the stretch wrap films is at least about150 g/mil, preferably at least about 200 g/mil, and more preferably fromat least about 250 g/mil.

The stretch wrap films of the present invention are preferablyconstructed so that the overall transverse direction tear resistance (TDtear), as determined by ASTM D1922, is at least about 450 g/mil,preferably at least about 500 g/mil, more preferably at least about 550g/mil. The machine direction tear resistance (MD tear) of the film isgenerally at least about 100 g/mil, preferably at least about 150 g/mil,and more preferably at least about 175 g/mil.

A parameter used to analyze the performance of stretch wrap films is thestress that results when the film is stretched to a desired percentageof its original length. This stress is indicative of the load retentioncharacteristics of the film and is determined in accordance with ASTMD882. The films of the present invention generally have a stress levelat 200% elongation of at least about 1700 psi, preferably at least about1850 psi, and more preferably at least about 2000 psi. The films of thepresent invention generally have a stress level at 250% elongation of atleast about 1800 psi, preferably at least about 1950 psi, morepreferably at least about 2100 psi.

The stretch wrap film of this invention can, if desired, be provided inthe non-stretched, i.e., unoriented, or at most only modestly stretched,state prior to use. The films of the present invention are capable ofbeing stretched from at least about 340%, preferably at least about 370%and more preferably at least about 400%.

The multilayer films of the present invention exhibit improvedouter/outer film slip characteristics. The slip properties of the filmsare reported as coefficient of friction (COF) values in accordance withASTM-D1894. The films generally have a kinetic COF value of below about1.0, preferably below about 0.8, and more preferably below about 0.6.

The films of the present invention generally have a gloss of at leastabout 88% and a haze of below about 2%.

The film configurations are constructed according to conventionalpractices. One preferred processing technique is to coextrude and castthe films in a simultaneous fashion, however in some cases it may beappropriate to first coextrude at least two film layers and thereafterextrusion coat the remaining film layers. Conventional techniques ofcoextrusion may be employed to assemble the composite structures of thefilms of this invention. Reference may be made to U.S. Pat. No.3,748,962, the contents of which are incorporated herein by reference inits entirety, for details of a coextrusion procedure which can beemployed in the fabrication of a multilayer film in accordance with thisinvention.

Generally, the resin materials are heated to their molten state andtheir viscosities are coordinated to prepare multilayer films in auniform manner. The molten materials are conveyed to a coextrusionadapter that combines the molten materials to form a multilayercoextruded structure. The layered polymeric material is transferredthrough an extrusion die opened to a predetermined gap commonly in therange of between about 0.05 in. (0.13 cm) and about 0.012 in. (0.03 cm).The material is then drawn down to the intended gauge thickness by meansof a primary chill or casting roll maintained at about 60 to about 130°F. (15-55° C.). Typical draw down ratios range from about 5:1 to about40:1.

The overall thickness of the stretch wrap film can vary widely accordingto end use specifications, but is generally in the range of the typicalthicknesses for stretch wrap films. Conventional for such films is athickness of from about 0.4 to about 3 mils, and is applicationspecific.

The pallet unitizing techniques described in U.S. Pat. Nos. 3,986,611and 4,050,221 are contemplated herein. The disclosures of these patentsare incorporated herein by reference in their entirety.

EXAMPLES

The following examples were conducted to demonstrate various aspects ofthe multilayer films of the present invention. The procedures utilizedin the following examples are set forth in Table 1.

                  TABLE 1    ______________________________________    STRETCH FILM TEST PROCEDURES    TEST PROCEDURE    ASTM TEST METHOD    ______________________________________    Tensile Yield Machine                      D882    Direction (MD)    Tensile Ultimate MD                      D882    Tensile Elongation MD                      D882    Tensile Force @    200% Stretch      D882    250% Stretch      D882    300% Stretch      D882    350% Stretch      D882    Elmendorf Tear MD D1922    Elmendorf Tear Transverse                      D1922    Direction (TD)    Total Energy Dart Drop                      D4272    F-50 Dart Drop    D1709    Gardner Gloss     D2457    Gardner Haze      D1003    Coefficient of Friction                      D1894    Instron Peel Cling                      D5458    Instron Probe Puncture Energy                      --    ______________________________________

The probe puncture energy test was conducted by use of an InstronUniversal tester that records a continuous reading of the force (stress)and penetration (strain) curve. A 6 in. by 6 in. film specimen issecurely mounted to a compression load cell to expose a 4 in. by 4 in.area. A hemispherically shaped (1 in. dia.) stainless steel probe,traveling at a constant speed of 10 in./min. is lowered into the film. Astress/strain curve is recorded and plotted. Peak force is the maximumforce encountered. The machine is used to integrate the area under thecurve, which is indicative of the energy consumed during the penetrationto rupture testing of the film. The probe penetration was also recordedin this test.

The films were also tested for performance in a stretch wrapper todetermine various film properties that occur during the stretchingoperation. The testing was conducted at rates similar to those employedby commercial equipment. The film width was 20 inches for this testmachine. The machine direction (MD) force at 200%, and maximum stretchand force values at breakage, were determined.

The films of the Examples were prepared using a pilot scale commercialcast film line machine. The material melt temperatures ranged from about480 to about 580° F. and were chosen to match melt viscosities of thevarious resins. The melts were conveyed to a coextrusion adapter thatcombines the melt flows into a multilayer coextruded structure. Thislayered flow was distributed through a single manifold film extrusiondie to the required width. The die gap opening was nominally 0.025inches. The material was drawn down to the final gauge. The materialdraw down ratio was about 31:1 for the 0.8 mil films. A vacuum box wasused to pin the melt exiting the die opening to a primary chill rollmaintained at about 90° F.

EXAMPLES

The results of the tests appear in Tables 2 and 3. Specifically, Table 2illustrates comparative films 1-5 and cling-cling inventive films 6-11,while Table 3 illustrates comparative films 1-5 and cling-slip inventivefilms 12-14. The inventive films were all coextuded in a three layeredembodiment of either an A/BC/A construction (films 6-11) or an A/BC/Dconstruction (films 12-14).

Referring to Table 2, the first and second layers (layers A) of theinventive films 6-11 comprised a 3.3 melt index (MI) linear low densitypolyethylene ("LLDPE") resin having a density of 0.918 g/cm³. The innerpolymeric layer (layer BC) of the inventive films 6-11 comprised ahomogeneous blend of resin B and resin C. Resin B of the inner polymericlayer of each inventive film comprised a 100% metallocene-catalyzed lowpolydispersity polymer. Specifically, resin B comprised ametallocene-catalyzed 3.4 LLDPE ("mLLDPE") resin having a density of0.918 g/cm³ that was prepared with a 1-hexene copolymer. In inventivefilms 6-8, resin C comprised a 1.9 MI high pressure, low densitypolyethylene ("HPLDPE") resin having a density of 0.921 g/cm³. However,in inventive films 9-11, resin C comprised a 3.3 MI HPLDPE resin havinga density of 0.923 g/cm³.

Referring to Table 3, inventive films 12-14 were constructed in a threelayer embodiment of A/BC/D. An outer high cling layer (layer A) ofinventive films 12-14 comprised a 5.0 MI ethylene-acrylate (EA)copolymer having a density of 0.945 g/cm (see "EA Copoly" in Table 3).The inner polymeric layer (layer BC) of inventive films 12-14 compriseda homogenous blend of resin B and resin C. Resin B comprised a 3.4 MImLLDPE resin having a density of 0.918 g/cm³ and resin C comprised a 3.3MI HPLDPE resin having a density of 0.923 g/cm³. Layer D comprised a 4.0MI LLDPE resin having a density of 0.940 g/cm³.

Comparative film 1 was comprised entirely of a 3.3 MI LLDPE having adensity of 0.918 g/cm³. Comparative films 2 and 3 were comprisedentirely of a resin B. Specifically, comparative film 2 comprised a 3.4MI mLLDPE having a density of 0.918 g/cm³, and comparative film 3comprised a 2.5 mLLDPE having a density of 0.917 g/cm³.

Comparative films 4 and 5 were comprised of an A/B/A construction.Comparative film 4 included a first and a second layer (layers A)comprised of a 3.3 MI LLDPE having a density of 0.918 g/cm³ and an innerpolymeric layer (layer B) comprised of 2.35 MI LLDPE having a density of0.9175 g/cm³. Comparative film 5 included a first and second layer(layers A) comprised of a 3.3 MI LLDPE having a density of 0.918 g/cm³and an inner polymeric layer (layer B) comprised of 3.4 MI mLLDPE havinga density of 0.918 g/cm³.

The compositions of each layer are shown as a total percent of all thelayers. For example, in Table 2, layer A comprised about 20 wt. % of thestretch wrap film in inventive film 6, in which each of the first andsecond layers were approximately 10 wt. % of the stretch wrap film.However, the proportions of the first and second layers (layers A) ofthe inventive films do not necessarily need to be equal. All of theinventive films (films 6-14), as well as the comparative films (films1-5), were constructed at the same gauge of about 0.8 mil.

Referring specifically to Table 2, inventive films 6-11 showedsignificant improvement in maximum stretch % over comparative films 2, 3and 5. Inventive films showed an improvement in maximum stretch % overcomparative films 1 and 4. These improvements in maximum stretch % inthe inventive films 6-11 as compared to the comparative films 1-5 wereunexpected. Inventive films 6-11 showed a slight improvement in clingproperties (see "unstretched cling I/O inside/outside!") overcomparative films 1, 4 and 5 and showed a great improvement overcomparative films 2 and 3.

All of the inventive films (films 6-11) in Table 2 had a good transversedirectional tear resistance (TD tear) relative to the machinedirectional tear resistance (MD tear). It is important to have a good TDtear relative to a MD tear under stretched conditions. Without thisbalance of MD and TD tear, the film catastrophically fails if any defectis present. Generally speaking, the TD tear of a stretch wrap filmshould have a value about two times greater than the MD tear andpreferably about three times greater than the MD Tear. As shown in Table2, comparative films 2, 3 and 5 do not have good TD tear to MD tearratios.

The inventive films 6-11 exhibited a much better puncture resistance, asmeasured by the F-50 dart drop test, than the comparative films 1 and 4.The inventive films 6-11 had a lower puncture resistance than thecomparative films 2, 3 and 5. However, comparative films 2 and 3 with asingle layer of metallocene-catalyzed LLDPE are not desirable for use asstretch wrap film due to their poor cling performance, low TD tearrelative to the MD tear, and poor maximum stretch values. As discussedabove, comparative film 5 does not have a good TD tear relative to MDtear and a good maximum stretch %.

Referring to Table 3, the inventive films 12-14 showed similarimprovements as the inventive films 6-11 when compared to thecomparative films 1-5. Inventive films 12-14 showed an excellent maximumstretch %, TD tear to MD tear ratio, cling properties and punctureresistance as measured by the F-50 dart drop test.

                                      TABLE 2    __________________________________________________________________________            Comparative Films        Inventive Films            SAMPLE No.            1    2    3    4    5    6    7    8    9    10   11    __________________________________________________________________________    Average Gauge            0.80 0.80 0.80 0.80 0.80 0.80 0.80 0.80 0.80 0.80 0.80    (mils)    Layer   A    B    B    A/B/A                                A/B/A                                     A/BC/A                                          A/BC/A                                               A/BC/A                                                    A/BC/A                                                         A/BC/A                                                              A/BC/A    Configuration    Resin "A" wt. %            100  0    0    20   20   20   20   20   20   20   20    Resin "B" wt. %            0    100  100  80   80   76   72   64   76   72   64    Resin "C" wt. %            0    0    0    0    0    4    8    16   4    8    16    Resin "A" Resin            3.3 MI         3.3 MI                                3.3 MI                                     3.3 MI                                          3.3 MI                                               3.3 MI                                                    3.3 MI                                                         3.3                                                              3.3 MI            LLDPE          LLDPE                                LLDPE                                     LLDPE                                          LLDPE                                               LLDPE                                                    LLDPE                                                         LLDPE                                                              LLDPE    Resin "B" Resin                 3.4 MI                      2.5 MI                           2.35 MI                                3.4 MI                                     3.4 MI                                          3.4 MI                                               3.4 MI                                                    3.4 MI                                                         3.4                                                              3.4 MI                 mLLDPE                      mLLDPE                           LLDPE                                mLLDPE                                     mLLDPE                                          mLLDPE                                               mLLDPE                                                    mLLDPE                                                         mLLDPE                                                              mLLDPE    Resin "C" Resin                  1.9 MI                                          1.9 MI                                               1.9 MI                                                    3.3 MI                                                         3.3                                                              3.3 MI                                     HPLDPE                                          HPLDPE                                               HPLDPE                                                    HPLDPE                                                         HPLDPE                                                              HPLDPE    LAB ANALYSIS    MD Ultimate            5,051.0                 8,441.0                      8,608.0                           5,876.0                                6,984.0                                     6,259.0                                          5,421.0                                               5,720.0                                                    6,565.0                                                         5,572.0                                                              5,208.0    (psi)    MD Elongation            588.0                 579.0                      630.0                           580.0                                639.0                                     620.0                                          585.0                                               599.0                                                    645.0                                                         605.0                                                              601.0    (%)    MD Stress @            1,596.0                 1,655.0                      1,701.0                           1,619.0                                1,586.0                                     1,702.0                                          1,819.0                                               2,107.0                                                    1,720.0                                                         1,843.0                                                              2,051.0    200% (psi)    MD Stress @            1,633.0                 N.A. N.A. 1,676.0                                1,689.0                                     1,781.0                                          1,908.0                                               2,214.0                                                    1,786.0                                                         1,914.0                                                              2,125.0    250% (psi)    MD Stress @            1,712.0                 N.A. N.A. 1,839.0                                1,887.0                                     2,004.0                                          2,112.0                                               2,428.0                                                    2,001.0                                                         2,112.0                                                              2,307.0    300% (psi)    MD Stress @            2,025.0                 N.A. N.A. 2,176.0                                2,156.0                                     2,275.0                                          2,395.0                                               2,720.0                                                    2,250.0                                                         2,353.0                                                              2,545.0    350% (psi)    MD Tear 266  378  353  254  359  292  239  111  289  220  130    (grams/mil)    TD Tear 768  557  491  728  542  652  675  744  635  633  699    (grams/mil)    Probe Punct.            9.9  13.3 14.2 12.7 20.5 12.3 17.6 14.8 14.2 14.0 14.3    Energy (in-lbs)    Probe Penetration            3.8  4.1  4.2  4.2  N.A. 3.8  3.9  4.1  4.2  4.2  4.2    (in)    F-50 Dart Drop            122  611  792  156  496  499  390  341  483  416  315    (g/mil)    Unstretched Cling            238.1                 86.6 80.5 230.6                                234.9                                     255.8                                          250.7                                               262.2                                                    264.8                                                         266.8                                                              282.3    I/O (g/in)    Film Gloss %            92.6 89.5 88.2 91.9 88.3 92.7 92.4 91.9 91.6 91.4 91.4    Film Haze %            1.76 2.60 2.18 1.55 2.06 1.55 1.57 1.58 1.68 1.61 1.53    STRETCH    WRAP TESTER    MD Force @            2.14 1.95 1.85 1.76 2.15 1.95 2.13 2.31 1.99 2.00 2.35    200% (lbs/in)    Maximum Force            2.67 2.21 2.28 2.32 2.41 2.64 2.84 2.97 2.60 2.73 2.97    (lbs/in)    Maximum Stretch            396  345  341  380  341  392  414  430  395  420  463    Defects/1500' @            78   6    N.A. 52   N.A. 2    6    10   1    0    2    300% Stretch    HS Tst F-50 Pot            W.N.R.                 3.11 N.A. 0.80 N.A. 2.25 2.35 1.65 3.30 1.00 2.05    Setting    HS Tst No Fail            N.A. 2.00 N.A. 0.00 N.A. 1.50 1.50 1.00 2.50 0.50 1.50    Pot Setting    __________________________________________________________________________

                                      TABLE 3    __________________________________________________________________________                  Comparative Films        Inventive Films                  SAMPLE No.                  1    2    3    4    5    12    13    14    __________________________________________________________________________    Average Gauge (mils)                  0.80 0.80 0.80 0.80 0.80 0.80  0.80  0.80    Layer Configuration                  A    B    B    A/B/A                                      A/B/A                                           A/BC/D                                                 A/BC/D                                                       A/BC/D    Resin "A" wt. %                  100  0    0    20   20.0 10    10    10    Resin "B" wt. %                  0    100  100  80   80.0 71.25 67.5  60    Resin "C" wt. %                  0    0    0    0    0    3.75  7.5   15    Resin "D" wt. %                  0    0    0    0    0    15    15    15    Resin "A" Resin                  3.3 MI         3.3 MI                                      3.3 MI                                           5 MI  5 MI  5 MI                  LLDPE          LLDPE                                      LLDPE                                           EA Copoly                                                 EA Copoly                                                       EA Copoly    Resin "B" Resin    3.4 MI                            2.5 MI                                 2.35 MI                                      3.4 MI                                           3.4 MI                                                 3.4 MI                                                       3.4 MI                       mLLDPE                            mLLDPE                                 LLDPE                                      mLLDPE                                           mLLDPE                                                 mLLDPE                                                       mLLDPE    Resin "C" Resin                        3.3 MI                                                 3.3 MI                                                       3.3 MI                                           HPLDPE                                                 HPLDPE                                                       HPLDPE    Layer "D" Resin                        0.940 g/cm.sup.3                                                 0.940 g/cm.sup.3                                                       0.940 g/cm.sup.3                                           LLDPE LLDPE LLDPE    LAB ANALYSIS    MD Ultimate (psi)                  5,051.0                       8,441.0                            8,608.0                                 5,876.0                                      6,984.0                                           4,677.0                                                 4,092.0                                                       4,709.0    MD Elongation (%)                  588.0                       579.0                            630.0                                 580.0                                      639.0                                           596.0 555.0 580.0    MD Stress @ 200% (psi)                  1,596.0                       1,655.0                            1,701.0                                 1,619.0                                      1,586.0                                           1,743.0                                                 1,871.0                                                       2,248.0    MD Stress @ 250% (psi)                  1,633.0                       N.A. N.A. 1,676.0                                      1,689.0                                           1,805.0                                                 1,934.0                                                       2,323.0    MD Stress @ 300% (psi)                  1,712.0                       N.A. N.A. 1,839.0                                      1,887.0                                           1,973.0                                                 2,088.0                                                       2,474.0    MD Stress @ 350% (psi)                  2,025.0                       N.A. N.A. 2,176.0                                      2,156.0                                           2,188.0                                                 2,316.0                                                       2,700.0    MD Tear (grams/mil)                  266  378  353  254  359  226   179   105    TD Tear (grams/mil)                  768  557  492  728  542  579   567   524    Probe -Punct. Energy (in-lbs)                  9.9  13.3 14.2 12.7 20.5 17.8  18.5  16.6    Probe Penetration (in)                  3.8  4.1  4.2  4.2  N.A. 4.5   4.6   4.2    F-50 Dart Drop (g/mil)                  122  611  792  156  496  474   479   270    Unstretched Cling I/O (g/in)                  238.1                       86.6 80.5 230.6                                      234.9                                           372.6 339.0 352.7    Film Gloss %  92.6 89.5 88.2 91.9 88.3 82.4  81.8  82.3    Film Haze %   1.76 2.60 2.18 1.55 2.06 2.96  2.95  3.02    STRETCH WRAP TESTER    MD Force @ 200% (lbs/in)                  2.14 1.95 1.85 1.76 2.15 2.09  2.28  2.70    Maximum Force (lbs/in)                  2.67 2.21 2.28 2.32 2.41 2.60  2.54  2.95    Maximum Stretch %                  396  345  341  380  341.0                                           417   351   490    Defects/1500' @ 300% Stretch                  78   6    N.A. 52   N.A. 26    19    6    HS Tst F-50 Pot Setting                  W.N.R.                       3.11 N.A. 0.80 N.A. N.A.  N.A.  N.A.    HS Tst No Fail Pot Setting                  N.A. 2.00 N.A. 0.00 N.A. N.A.  N.A.  N.A.    __________________________________________________________________________

What is claimed is:
 1. A method for wrapping an article,comprising:wrapping the article with a multilayer, thermoplastic stretchwrap film containing at least three polymeric film layers, said filmcomprising(a) a first layer comprising a polymer of two or moremonomers, wherein the first monomer is ethylene, in a major amount byweight, and the second monomer is an alpha olefin of from about 3 toabout 12 carbon atoms, in a minor amount by weight; (b) a second layercomprising a polymer of two or more monomers, wherein the first monomeris ethylene, in a major amount by weight, and the second monomer is analpha olefin of from about 3 to about 12 carbon atoms, in a minor amountby weight, at least one of said first layer and said second layer hassufficient cling resulting from inherent cling alone, cling additive ora combination thereof so as to produce a cling force to the other layerof at least about 140 grams/inch as determined by ASTM D5458-94; and (c)at least one inner polymeric layer, located between said first layer andsaid second layer, comprising a blend of a low polydispersity polymerand either a high pressure low density polyethylene resin, a very lowdensity polyethylene resin or combinations thereof, said lowpolydispersity polymer having a polydispersity of from about 1 to about4, a melt index (I₂) of from about 0.5 to about 10 g/10 min., a meltflow ratio (I₂₀ /I₂) of from about 12 to about 22 and comprising atleast about 70 wt. % of the total amount of said inner polymericlayer(s), said high pressure low density polyethylene resin having amelt index (I₂) of from about 1 to about 10 g/10 min. and a density offrom about 0.9 to about 0.935 g/cm³, said very low density polyethyleneresin having a melt index (I₂) of from about 0.5 to about 5 g/10 min,and a density of from about 0.880 to about 0.912 g/cm³ ; so as toproduce a stretch wrap film having a maximum stretch of at least 340%,and an F-50 dart drop value of at least about 150 g/mil as determined byASTM D1709, and whereby said stretch wrap film is stretched during thewrapping step.
 2. The method of claim 1 wherein said stretch wrap filmcomprises at least about 60 wt. % of the total amount of said innerpolymeric layer(s).
 3. The method of claim 2 wherein said stretch wrapfilm comprises at least about 70 wt. % of the total amount of said innerpolymeric layer(s).
 4. The method of claim 1 wherein said polydispersityis in the range of from about 1.5 to about
 4. 5. The method of claim 4wherein said polydispersity is in the range of from about 2 to about 4.6. The method of claim 5 wherein said polydispersity is in the range offrom about 2 to about
 3. 7. The method of claim 1 wherein the density ofsaid low polydispersity polymer is in the range of from about 0.88 toabout 0.93 g/cm³.
 8. The method of claim 7 wherein the density of saidlow polydispersity polymer is in the range of from about 0.88 to about0.925 g/cm³.
 9. The method of claim 1 wherein the melt index of said lowpolydispersity polymer is in the range of about 0.5 to about 5 g/10 min.10. The method of claim 9 wherein the melt index of said lowpolydispersity polymer is in the range of about 0.5 to about 2 g/10 min.11. The method of claim 1 wherein the melt flow ratio of said lowpolydispersity polymer is in the range of from about 14 to about
 20. 12.The method of claim 11 wherein the melt flow ratio of said lowpolydispersity polymer is in the range of from about 16 to about
 18. 13.The method of claim 1 wherein said low polydispersity polymer is madewith a metallocene catalyst.
 14. The method of claim 1 wherein at leastone of said first layer and said second layer has a cling force to theother layer of at least about 180 grams/inch.
 15. The method of claim 14wherein at least one of said first layer and said second layer has acling force to the other layer of at least about 200 grams/inch.
 16. Themethod of claim 15 wherein at least one of said first layer and saidsecond layer has a cling force to the other layer of at least about 220grams/inch.
 17. The method of claim 1 wherein at least one of said firstlayer and said second layer has a cling force to the other layer in therange from about 140 to about 280 grams/inch.
 18. The method of claim 1wherein the F-50 dart drop value of the stretch wrap film is at leastabout 200 g/mil.
 19. The method of claim 18 wherein the F-50 dart dropvalue of the stretch wrap film is at least about 250 g/mil.
 20. Themethod of claim 1 wherein the transverse direction tear resistance ofthe stretch wrap film is at least about 450 g/mil.
 21. The method ofclaim 20 wherein the transverse direction tear resistance of the stretchwrap film is at least about 500 g/mil.
 22. The method of claim 21wherein the transverse direction tear resistance of the stretch wrapfilm is at least about 550 g/mil.
 23. The method of claim 1 wherein themachine direction tear resistance of the stretch wrap film is at leastabout 100 g/mil.
 24. The method of claim 23 wherein the machinedirection tear resistance of the stretch wrap film is at least about 150g/mil.
 25. The method of claim 24 wherein the machine direction tearresistance of the stretch wrap film is at least about 175 g/mil.
 26. Themethod of claim 1 wherein the stretch wrap film has a machine directionstress level at 200% elongation of at least 1700 psi.
 27. The method ofclaim 26 wherein the stretch wrap film has a machine direction stresslevel at 200% elongation of at least 1850 psi.
 28. The method of claim27 wherein the stretch wrap film has a machine direction stress level at200% elongation of at least 2000 psi.
 29. The method of claim 1 whereinthe stretch wrap film has a machine direction stress level at 250%elongation of at least 1800 psi.
 30. The method of claim 29 wherein thestretch wrap film has a machine direction stress level at 250%elongation of at least 1950 psi.
 31. The method of claim 30 wherein thestretch wrap film has a machine direction stress level at 250%elongation of at least 2100 psi.
 32. The method of claim 1 wherein thesecond monomer of said first layer and said second layer areindependently selected from the group consisting of propylene, 1-butene,1-pentene, 1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-octene,1-decene, and 1-dodecene.
 33. The method of claim 32 wherein the secondmonomer of said first layer and said second layer are independentlyselected from the group consisting of 1-butene, 1-hexene, and 1-octene.34. The method of claim 1 wherein said low polydispersity polymercomprises a polyethylene copolymer or terpolymer.
 35. The method of 1wherein the stretch wrap film has a maximum stretch % of at least about370%.
 36. The method of 35 wherein the stretch wrap film has a maximumstretch % of at least about 400%.
 37. The method of claim 1 wherein themelt index of said high pressure low density polyethylene is from about1 to about 5 g/10 min.
 38. The method of claim 37 wherein the melt indexof said high pressure low density polyethylene is from about 1 to about2.5 g/10 min.
 39. The method of claim 1 wherein the density of said highpressure low density polyethylene is from about 0.915 to about 0.925g/cm³.
 40. The method of claim 1 wherein the melt index of said very lowdensity polyethylene is from about 1 to about 3 g/10 min.
 41. The methodof claim 1 wherein the density of said very low density polyethylene isfrom about 0.89 to about 0.91 g/cm³.
 42. The method of claim 1 whereinsaid stretch wrap film comprises from about 2 to about 30 wt. % of saidhigh pressure low density polyethylene resin.
 43. The method of claim 42wherein said stretch wrap film comprises from about 5 to about 15 wt. %of said high pressure low density polyethylene resin.
 44. The method ofclaim 1 wherein said stretch wrap film comprises from about 2 to about30 wt. % of said very low density polyethylene resin.
 45. The method ofclaim 44 wherein said stretch wrap film comprises from about 15 to about25 wt. % of said very low density polyethylene resin.
 46. The method ofclaim 1 further comprising an outer high cling layer located on asurface of said first layer opposite of said inner polymeric layer. 47.The method of claim 46 wherein said outer high cling layer has a clingforce to the second layer of at least about 300 grams/inch as determinedby ASTM D5458-94.
 48. The method of claim 47 wherein said outer highcling layer is chosen from the group consisting of an ethylene-acrylatepolymer and a very low density polyethylene.
 49. The method of claim 48wherein said very low density polyethylene of said outer high clinglayer has a density of from about 0.88 g/cm³ to about 0.912 g/cm³. 50.The method of claim 46 further comprising an outer slip layer located ona surface of said second layer opposite of said inner polymer layer. 51.The method of claim 50 wherein said outer slip layer is chosen from thegroup consisting of polyethylene, polypropylene and combinationsthereof.
 52. The method of claim 1 further comprising a second innerpolymeric layer located on a surface of the first inner polymeric layer.53. The method of claim 52 wherein said second inner polymeric layercomprises a blend of a low polydispersity polymer and either a highpressure low density polyethylene resin, a very low density polyethyleneresin or combinations thereof, said low polydispersity polymer having apolydispersity of from about 1 to about 4, a melt index (I₂) of fromabout 0.5 to about 10 g/10 min., and a melt flow ratio (I₂₀ /I₂) of fromabout 12 to about 22, said high pressure low density polyethylene resinhaving a melt index (I₂) of from about 1 to about 10 g/10 min. and adensity of from about 0.9 to about 0.935 g/cm³, said very low densitypolyethylene resin having a melt index (I₂) of from about 0.5 to about 5g/10 min, and a density of from about 0.880 to about 0.912 g/cm³.
 54. Amethod for wrapping an article, comprising:wrapping the article with amultilayer, thermoplastic stretch wrap film containing at least threepolymeric film layers, said film comprising(a) a first layer comprisinga polymer of two or more monomers, wherein the first monomer isethylene, in a major amount by weight, and the second monomer is analpha olefin of from about 3 to about 12 carbon atoms, in a minor amountby weight; (b) an outer high cling layer has sufficient cling resultingfrom inherent cling alone, cling additives or a combination thereof soas to produce a cling force to the first layer of at least about 300grams/inch as determined by ASTM D5458-94; and (c) at least one innerpolymeric layer, located between said first layer and said second layer,comprising a blend of a low polydispersity polymer and either a highpressure low density polyethylene resin, a very low density polyethyleneresin or combinations thereof, said low polydispersity polymer having apolydispersity of from about 1 to about 4, a melt index (I₂) of fromabout 0.5 to about 10 g/10 min., a melt flow ratio (I₂₀ /I₂) of fromabout 12 to about 22 and comprising at least about 70 wt. % of the totalamount of said inner polymeric layer(s), said high pressure low densitypolyethylene resin having a melt index (I₂) of from about 1 to about 10g/10 min. and a density of from about 0.9 to about 0.935 g/cm³, saidvery low density polyethylene resin having a melt index (I₂) of fromabout 0.5 to about 5 g/10 min, and a density of from about 0.880 toabout 0.912 g/cm³ ; so as to produce a stretch wrap film having amaximum stretch of at least 340%, and an F-50 dart drop value of atleast about 150 g/mil as determined by ASTM D1709, and whereby saidstretch wrap film is stretched during the wrapping step.
 55. The methodof claim 54 wherein said outer high cling layer is chosen from the groupconsisting of an ethylene-acrylate polymer and a very low densitypolyethylene.
 56. The method of claim 55 wherein said very low densitypolyethylene has a density of from about 0.88 g/cm³ to about 0.910g/cm³.
 57. A method for wrapping an article, comprisingwrapping thearticle with a multilayer, thermoplastic stretch wrap film containing atleast three polymeric film layers, said film comprising(a) an outer highcling layer; (b) an outer slip layer, said outer high cling force hassufficient cling resulting from inherent cling alone, cling additives ora combination thereof so as to produce a cling force to said outer sliplayer of at least about 300 grams/inch as determined by ASTM D5458-94;and (c) at least one inner polymeric layer, located between said outerslip layer and said outer high cling layer, comprising a blend of a lowpolydispersity polymer and either a high pressure low densitypolyethylene resin, a very low density polyethylene resin orcombinations thereof, said low polydispersity polymer having apolydispersity of from about 1 to about 4, a melt index (I₂) of fromabout 0.5 to about 10 g/10 min., a melt flow ratio (I₂₀ /I₂) of fromabout 12 to about 22 and comprising at least about 70 wt. % of the totalamount of said inner polymeric layer(s), said high pressure low densitypolyethylene resin having a melt index (I₂) of from about 1 to about 10g/10 min. and a density of from about 0.9 to about 0.935 g/cm³, saidvery low density polyethylene resin having a melt index (I₂) of fromabout 0.5 to about 5 g/10 min, and a density of from about 0.880 toabout 0.912 g/cm³ ; so as to produce a stretch wrap film having amaximum stretch of at least 340%, and an F-50 dart drop value of atleast about 150 g/mil as determined by ASTM D1709, andwhereby saidstretch wrap film is stretched during the wrapping step.
 58. The methodof claim 57 wherein said outer high cling layer is chosen from the groupconsisting of an ethylene-acrylate polymer and a very low densitypolyethylene.
 59. The method of claim 58 wherein said very low densitypolyethylene of said outer high cling layer has a density of from about0.88 g/cm³ to about 0.910 g/cm³.
 60. The method of claim 57 wherein saidslip layer is chosen from the group consisting of polyethylene,polypropylene and combinations thereof.
 61. A method for wrapping anarticle, comprising:wrapping the article with a multilayer,thermoplastic stretch wrap film containing at least three polymeric filmlayers, said film comprising(a) a first polymeric cling layer; (b) asecond polymeric cling layer; and (c) at least one inner polymericlayer, located between said first polymeric cling layer and said secondpolymeric cling layer, comprising a blend of a low polydispersitypolymer and either a high pressure low density polyethylene resin, avery low density polyethylene resin or combinations thereof, said lowpolydispersity polymer comprising a polyethylene copolymer or terpolymerhaving a polydispersity of from about 1 to about 4, a melt index (I₂) offrom about 0.5 to about 10 g/10 min., and a melt flow ratio (I₂₀ /I₂) offrom about 12 to about 22, said polyethylene copolymer or terpolymercomprising at least about 70 wt. % of the total amount of said innerpolymeric layer(s), said high pressure low density polyethylene resinhaving a melt index (I₂) of from about 1 to about 10 g/10 min. and adensity of from about 0.9 to about 0.935 g/cm³, said very low densitypolyethylene resin having a melt index (I₂) of from about 0.5 to about 5g/10 min, and a density of from about 0.880 to about 0.912 g/cm³ ;wherein said stretch wrap film comprises at least about 60 wt. % of thetotal amount of said inner polymeric layer(s); so as to produce astretch wrap film having a maximum stretch of at least 340%, and an F-50dart drop value of at least about 150 g/mil as determined by ASTM D1709,and whereby said stretch wrap film is stretched during the wrappingstep.
 62. The method of claim 61 wherein the first polymeric cling layerand the second polymeric cling layer comprise two or more monomers,wherein the first monomer is ethylene, in a major amount by weight, andthe second monomer is an alpha olefin of from about 3 to about 12 carbonatoms, in a minor amount by weight.
 63. The method of claim 61 whereinat least one of said first polymeric cling layer and said secondpolymeric cling layer has a cling force to the other layer of at leastabout 140 grams/inch as determined by ASTM D5458-94.
 64. The method ofclaim 63 wherein at least one of said first polymeric cling layer andsaid second polymeric cling layer has a cling force to the other layerof at least about 220 grams/inch.
 65. The method of claim 61 whereinsaid stretch wrap film comprises at least about 70 wt. % of the totalamount of said inner polymeric layer(s).
 66. The method of claim 61wherein said polydispersity is in the range of from about 1.5 to about4.
 67. The method of claim 61 wherein the density of said polyethylenecopolymer or terpolymer is in the range of from about 0.88 to about 0.93g/cm³.
 68. The method of claim 61 wherein the melt index of saidpolyethylene copolymer or terpolymer is in the range of about 0.5 toabout 2 g/10 min.
 69. The method of claim 61 wherein the melt flow ratioof said polyethylene copolymer or terpolymer is in the range of fromabout 14 to about
 20. 70. The method of claim 61 wherein saidpolyethylene copolymer or terpolymer is made with a metallocenecatalyst.
 71. The method of claim 61 wherein the F-50 dart drop value ofthe stretch wrap film is at least about 200 g/mil.
 72. The method ofclaim 61 wherein the transverse direction tear resistance of the stretchwrap film is at least about 500 g/mil.
 73. The method of claim 61wherein the machine direction tear resistance of the stretch wrap filmis at least about 150 g/mil.
 74. The method of claim 62 wherein thesecond monomer of said first polymeric cling layer and said secondpolymeric cling layer are independently selected from the groupconsisting of propylene, 1-butene, 1-pentene, 1-hexene,3-methyl-1-pentene, 4-methyl-1-pentene, 1-octene, 1-decene, and1-dodecene.
 75. The method of claim 61 wherein the stretch wrap film hasa machine direction stress level at 200% elongation of at least 1700psi.
 76. The method of claim 61 wherein the stretch wrap film has amachine direction stress level at 250% elongation of at least 1800 psi.77. The method of claim 61 wherein the stretch wrap film has a maximumstretch % of at least about 400%.
 78. The method of claim 61 wherein themelt index of said high pressure low density polyethylene resin is fromabout 1 to about 5 g/10 min.
 79. The method of claim 61 wherein thedensity of said high pressure low density polyethylene resin is fromabout 0.915 to about 0.925 g/cm³.
 80. The method of claim 61 wherein themelt index of said very low density polyethylene resin is from about 1to about 3 g/10 min.
 81. The method of claim 61 wherein the density ofsaid very low density polyethylene resin is from about 0.89 to about0.91 g/cm³.
 82. The method of claim 61 wherein at least one of saidinner polymeric layer(s) comprises from about 2 to about 30 wt. % ofsaid high pressure low density polyethylene resin.
 83. The method ofclaim 82 wherein at least one of said inner polymeric layer(s) comprisesfrom about 5 to about 15 wt. % of said high pressure low densitypolyethylene resin.
 84. The method of claim 61 wherein at least one ofsaid inner polymeric layer(s) comprises from about 2 to about 30 wt. %of said very low density polyethylene resin.
 85. The method of claim 84wherein at least one of said inner polymeric layer(s) comprises fromabout 15 to about 25 wt. % of said very low density polyethylene resin.86. A method for wrapping an article, comprising:wrapping the articlewith a multilayer, thermoplastic stretch wrap film containing at leastthree polymeric film layers, said film comprising(a) a first layercomprising a linear low density polyethylene resin, said linear lowdensity polyethylene resin has a density from about 0.89 to about 0.94g/cm³ and a melt index (I₂) of from about 1 to about 10 g/10 min., andcontains from about 2 to about 8 weight percent n-hexane extractables;(b) a second layer comprising a linear low density polyethylene resin,said linear low density polyethylene resin has a density from about 0.89to about 0.94 g/cm³ and having a melt index (I₂) of from about 1 toabout 10 g/10 min., and contains from about 2 to about 8 weight percentn-hexane extractables, said first layer and said second layer has acling force to the other layer of at least about 140 grams/inch asdetermined by ASTM D5458-94; and (c) at least one inner polymeric layer,located between said first layer and said second layer, comprising ablend of a low polydispersity polymer and either a high pressure lowdensity polyethylene resin, a very low density polyethylene resin orcombinations thereof, said low polydispersity polymer comprising apolyethylene copolymer or polyethylene having a polydispersity of fromabout 1 to about 4, a melt index (I₂) of from about 0.5 to about 10 g/10min., and a melt flow ratio (I₂₀ /I₂) of from about 12 to about 22, saidpolyethylene copolymer or terpolymer comprising at least about 70% wt. %of the total amount of said inner polymeric layer(s), said high pressurelow density polyethylene resin having a melt index (I₂) of from about 1to about 10 g/10 min. and a density of from about 0.9 to about 0.935g/cm³, said very low density polyethylene resin having a melt index (I₂)of from about 0.5 to about 5 g/10 min, and a density of from about 0.880to about 0.912 g/cm³ ; wherein said stretch wrap film comprises at leastabout 60 wt. % of the total amount of said inner polymeric layer(s); soas to produce a stretch wrap film having a maximum stretch of at least340%, and an F-50 dart drop value of at least about 150 g/mil asdetermined by ASTM D1709, and whereby said stretch wrap film isstretched during the wrapping step.
 87. The method of claim 57 furtherincluding a first layer located between said inner polymeric layer andsaid outer slip layer.
 88. The method of claim 1 wherein said inherentcling is partially from n-hexane extractables.
 89. The method of claim 1wherein said cling force is partially from at least one cling additive.90. The method of claim 89 wherein said cling additive ispoly-isobutylene.
 91. The method of claim of claim 1 wherein said firstlayer and said second layer are independently selected from the groupconsisting of linear low density polyethylene, very low densitypolyethylene, high pressure low density polyethylene, ethylene-acrylatepolymers and mixtures thereof.
 92. The method of claim 54 wherein saidinherent cling is partially from n-hexane extractables.
 93. The methodof claim 54 wherein said cling force is partially from at least onecling additive.
 94. The method of claim 57 wherein said inherent clingis partially from n-hexane extractables.
 95. The method of claim 57wherein said cling force is partially from at least one cling additive.96. The method of claim 61 wherein said inherent cling is partially fromn-hexane extractables.
 97. The method of claim 61 wherein said clingforce is partially from at least one cling additive.
 98. The method ofclaim 97 wherein said cling additive is poly-isobutylene.
 99. The methodof claim 61 wherein said first polymeric cling layer and said secondpolymeric cling layer are made from olefin polymer resins.
 100. Themethod of claim 99 wherein at least one of said olefin polymer resins isa copolymer, said copolymer comprising an olefin monomer with a secondmonomer.
 101. The method of claim 100 wherein said olefin polymer resinis an ethylene-acrylate polymer, said ethylene-acrylate polymer beingselected from the group consisting of methyl, ethyl, and n-butylacrylate.
 102. The method of claim 61 wherein said first polymeric clinglayer and said second polymeric cling layer are independently selectedfrom the group consisting of linear low density polyethylene, very lowdensity polyethylene, high pressure low density polyethylene,ethyleneacrylate polymers and mixtures thereof.
 103. The method of claim102 wherein the acrylate of said ethylene-acrylate polymers is selectedfrom the group consisting of methyl, ethyl and n-butyl acrylate. 104.The method of claim 61 wherein said stretch wrap film has a maximumstretch of at least about 360%.
 105. The method of claim 104 whereinsaid stretch wrap film has a maximum stretch of at least about 380%.